1. Field of the Invention
This invention relates to a method for the production of a sulfide group-containing thiol compound. More particularly, this invention relates to a method for the production of a sulfide group-containing thiol compound by the ring-opening addition of alkylene sulfide to a thiol compound.
The sulfide group-containing thiol compounds which are obtained by the method of this invention are useful compounds which find extensive utility such as in chelating agents, lubricant additives, additives for rubber, additives for refined petroleum oils, and polymerization chain transfer agents.
2. Description of the Prior Art
As means for producing a sulfide group-containing thiol compound by the ring-opening addition of alkylene sulfide to a thiol compound, a method which effects the reaction in the absence of a catalyst has been heretofore disclosed in DE-A-696, 774. Since this method requires a high temperature, however, U.S. Pat. No. 2,490,984 has proposed a method which uses boron trifluoride as a catalyst for the reaction and U.S. Pat. No. 2,497,100 a method which uses sodium alkoxide by way of improvement. Methods which similarly use alkali metal alkoxides have been also proposed in J. Am. Chem. Soc. (1947), Vol. 69, page 2675-2677, J. Chem. Soc. (1948), page 1894-1895, and J. Chem. Soc. (1949), page 282-287. Though these catalysts are highly active, they are at a disadvantage in manifesting low selectivity for the products aimed at because they are liable, when taking part in a reaction using ethylene sulfide, to induce the polymerization of ethylene sulfide.
A case of study using triethyl amine as a catalyst has been reported in Izv. Akad. Nauk, SSSR, Ser. Khim. (1975), No. 3, page 660-662. Then, U.S. Pat. No. 4,163,832 discloses a method which similarly uses either such amine compounds as trimethyl amine and triethyl amine or trimethyl phosphine. Further, J. Fluorine Chem. (1975), Vol. 6, page 145-159 discloses a reaction of pentafluorothiophenol with ethylene sulfide by the use of pyridine. When amine compounds and pyridines are used as a catalyst, they indeed go to improve the selectivity for a relevant reaction. When the reaction involves a thiol compound with low reactivity or alkylene sulfide other than ethylene sulfide, however, this catalyst is at a disadvantage in lowering the reaction velocity. Moreover, since the thiol compound is weakly acidic, the basic amine catalyst which exists in the system poses the problem that it is not thoroughly separated and removed with ease even by the distillation.
JP-B-07-5,585 has disclosed a method for effecting the reaction in a sodium hydroxide-benzene type aqueous solution with benzyl trimethyl ammonium chloride as a catalyst. This method, however, is deficient in yield and selectivity. The use of this quaternary ammonium compound as a catalyst is at a disadvantage in easily inducing the polymerization of alkylene sulfide due to the presence of water in a two-phase system and in not being applicable to a thiol compound containing an easily hydrolyzable ester group.
As means for producing a sulfide group-containing mercaptocarboxylic ester, Chem. Pharm. Bull., 38(11), pp. 3035-3041 (1990) has disclosed a method for implementing the production by causing ethane-1,2-dithiol to react with chloroacetic ester in the presence of triethyl amine. This method, however, is deficient in economic usefulness because it gives rise to a by-product containing halogen. Japan Chemical Journal, Vol. 81, pp. 328-331 (1960) teaches to obtain an ester by causing ethanol to react with the reaction product of .beta.-propiolactone with ethane-1,2-dithiol. This method forms by-products copiously and suffers a poor yield. Eur. Polym. J., 7, pp. 189-201 (1971) reports a method for polymerizing propylene sulfide by using mercaptopropionic acid as a chain transfer agent. The product obtained by this reaction is a polymer. This reaction has been incapable of obtaining such a low adduct as with the number of mols of added alkylene sulfide in the approximate range of 1 to 3.
It is, therefore, an object of this invention to provide a novel method for the production of a sulfide-containing thiol compound.
Another object of this invention is to provide a method for the production of a sulfide group-containing thiol compound by the use of a catalyst which can manifest high activity fit for various thiol compounds, avoid inducing the polymerization of alkylene sulfide, and promote the ring-opening addition reaction with high selectivity.
Further object of this invention is to provide a novel method for the production of a sulfide group-containing mercaptocarboxylic ester.
Furthermore object of this invention is to provide a method for the production of a sulfide group-containing mercaptocarboxylic ester by the use of a catalyst capable of proceeding the reaction by the ring-opening addition with high selectivity without inducing the polymerization of an alkylene sulfide.